Fuel may be injected to an internal combustion engine via port fuel injectors and direct fuel injectors. The port fuel injectors may improve fuel atomization during cold conditions and provide a longer duration for injecting fuel to combust during a cylinder cycle. The direct fuel injectors may increase cylinder charge cooling so that the possibility of engine knock may be reduced. Port and direct fuel injectors may be deployed in boosted engines to help extend the engine's dynamic speed and torque range. However, at lower to middle engine loads, it may be more difficult to control the engine's air fuel ratio because small changes in a small amount of fuel desired to be injected to a cylinder may provide larger undesirable changes in engine air-fuel ratio. Further, changes in an estimated amount of air inducted to a cylinder after fuel delivery is scheduled for the cylinder may lead for further engine air-fuel ratio variation from a desired engine air-fuel ratio.
The inventors herein have recognized the above-mentioned disadvantages and has developed an engine fueling method, comprising: port injecting fuel to a cylinder in a cylinder cycle via a first fuel pulse width, the first fuel pulse width adjusted responsive to engine operating conditions after being scheduled for delivery; and directly injecting fuel to the cylinder in the cylinder cycle via a second fuel pulse width, the second fuel pulse width selectively adjusted after being scheduled for delivery.
By adjusting a port fuel injection amount in response to changes in engine operating conditions during a cylinder cycle, it may be possible to provide the technical result of adjusting a port fuel injection amount to meet a changing desired cylinder fuel amount. Further, an amount of directly injected fuel may also be adjusted to meet changes in desired fuel amount, even after intake valve closing, so that a sum of port injected fuel and direct injected fuel amounts more closely matches a desired cylinder fuel amount.
The present description may provide several advantages. In particular, the approach may improve engine air-fuel ratio control. Additionally, the approach may provide an improved way to adjust direct fuel injection pulse widths after port fuel injection pulse widths have been adjusted after being scheduled. Further, the approach provides for a systematic way of operating direct and port fuel injectors.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.